Inverse neutral telegraph repeater concentration group cord and attendant&#39;s circuit



June 27, 1944.

INVERSE NEUTRAL W. V. K. LARGE ETAL GROUP CORD AND ATTENDANTS CIRCUIT Filed March 1l, 1941 TELEGRAH REPETER CONCENTRATION 4 'Sheets-Sheet l A 7' TOR/VE Y 2,352,272 ER CONCENTRATION s CIRC rch l1. 1941 UIT 4 Sheets-Sheet 2 June 27, 1944l w. v. K. LARGE ETAL INVERSE NEUTRAL TELEGRAPH REPEAT G ROUP CORD AND ATTENDANT Filed Ma MA Rc/NAL 206 F nt E /ARs/NAL T; MA; Ram/AL 2/0 POLAR/Eo June 27,` 1944. w v. K. LARGE ETAL INVERSE NEUTRAL TELEGRAPH REPEATER CONCENTRATIO GROUP CORD AND ATTENDANTS CIRCUIT Filed Marh 11, 1941 4 Sheets-Sheet /N SER/EJ` THRU CONTAC f6' AND ARMA 7' U/PES 0F CORRESPOND/NG KEYS IN PRECED/NG COPDS.

l4r rom/EV Jai/JM June 27, 1944. .v K. LARGE ET AL n I 2,352,272

INVERSE NEUTRAL TELEGRAPH REPEATER CONCENTRATION f GROUP CQRD AND ATTENDANTS CR'UII" ,Filed March ll, 1941 A{Sheets-Shea?. 4

3/ T 'T-Eypfh/R/TE? POLAR/zw gillll 1 m wr. ARGE mvg/vrom: anfLucs/r y third connects the subscribers loop circuit to local loop circuit is closed. The two ends of the loop are terminated in battery arranged in series-aiding relationship. The magnet of sounder |25 is energized, attracting its armature. The effect of current through the left-hand winding of relay |22 is balanced by the effect of current f flowing through the right-hand Winding so that the hub. This circuit is traced in detail and explained below under the heading .Recep'tion ofy signals from west line. The armature of relay is held in engagement with its right-hand or marking contact by the effectr of current in the West receiving line loop andthewinding of relay |0| during marking. "Relay |05 is in the operated condition due to current flowing over a path from negative battery through the winding of relay |05, the left-hand innermost armature and back contact of relay |00, left-hand back contact and armature of relay ||3 to ground.

Relays |05, |06', ||3.'a`nd*||4 and thecorrespending relays ||5, H6,l andl ||8 in the east line are relays which condition a concentration group for either half or full duplex operation. Since the concentration group per Fig. 1 is arranged for halfduplex operation, these relays assume' the conditions shown'when the concentration is established and remain in such condition indefinitely unless. the concentration is changed.

The manner in -which concentration groups are established and changed is described in the above application perSerial No. 362,548. Since it does not form part of this invention. these operations will not be described herein. For the purposes of this disclosure it should be suicient to call attention to 'the' fact that relays such as |05, |06, ||3 and l||l|| and theirequivalents in other lines remain in the-condition shown while a half duplex inverse neutral concentration is established. Relays |03, ||9 and A|20 are used in disconnecting the line or loop with which each is associated from the concentration group for testing purposes.

The armature of relay is held in engage ment with its right-hand orl markingl contact while the concentration group is in the idle condition or during marking due to the effect of current iiowing through its top winding over an obvious circuit. The effect of this current is u nopposed as no current flows through the bottom` winding of relay since both ends of the circuit extending through the bottom winding of relay are terminated in negative battery of the same magnitude. g I'I'he armaturejof relay 0.

is held in engagement with its left-hand contact during the marking periodbythe eiect of current flowing through its top orline winding, which effect preponderates over the effect of current ilowing in its bottom .-'Windingover a circuit from negative battery, through the righthand contact and armature of relay through the bottom Winding of relay |0 and the artificial line, indicated by rectangle |42|, to ground, Ztending to operate the varmature'or relay ||0 to vengage with its right-hand or spacing'contact.

While the concentration group is in the marking condition, no current flows through the top winding of relay ||2 vand the Yarmature of this relay is held in engagement with its right-hand' or marking contact by the effect of current flowing through its bottom winding from the lefthand or marking contact andk armature oi relay 0.

In thev marking condition "the vsubscribersv the armature of relay |22 remains in the condi- ;tions shown. `The eiect of the loop current ow- 'ingthroughthe top winding of relay |23 tending to actuate the armature of relay |23 towards iits. left-hand orimarking contact preponderates over the effect of current flowing through the bottom winding from the left-hand or marking contact and armature of relay |24 and the arvmature of relay |23 is held in engagement with `its left-hand or marking contact. 'I'he armature of relay |24 is held in engagement with its left-hand or marking contact, due to the effect ofcurrent iiowing through its top Winding. This effect is unopposed as no current flows through the bottom winding of relay |24 as the ends of the vcircuit extending through the bottom winding of relay |24 are `terminated in battery of the same polarity and magnitude.

i Receptionof signals from west line As telegraph signals are received from the west line the armature of relay |0| is actuated between its rightand left-hand contacts. When the armature is on itsright-hand contact a circuit may be traced vfrom negative battery through the right-hand contact and armature of relay |0|, through the bottom Winding of re lay |02 to ground.. The armature of relay |02 is actuated to its right-hand contact. When the armature of relay |02 is in engagement with its right-hand contact a circuit may be traced A from negative battery through the bottom windings of relays |03 and |04, bottom armature and make contact of relay |05, topwinding of relay 02, top frontcontact and armature of relay |05, right-hand contactand armature of relay |02,

left-hand outermost armature and back contact of relay |06, resistance |01, armature and contact ofrelay |08 tothe hub |09.

From-the hub the circuit extends in parallel branches into the line east and the subscribers m line.

contact of relay ||2, top armature and front contact of relay ||5, top Winding of relay ||2, bottom front contact and armature of relay ||5 and through the-bottom Winding of relay to negative battery. The branch extending into l the subscribers line extends through the contact and armature of relay |20, resistance |21, armature and left-hand 'contact of relay |23, bottom winding'of'relay |24'to negative battery.

1t should be observed that all of these branches,

' namely the branch in the line west, that in the line' east and the branch into the subscribers line, all of which radiate from the hub of the concentration |09 are terminated in battery of the same polarity and magnitude, so that no current flows in any of these branches forthe marking condition.

Since no current flows in the branch which connects the east line to the hub |09 the bottom winding of relay will not be energized when a marking signal is received from the west line.

Under this condition, as explained above, the current in the top or biasing Winding of relay |'|-|V 'maintains its armature in engagement With its right-hand or marking contact. Negative battery is therefore connected through the right-I hand contact and armature of relay I I and the top winding of relay |`0 to transmit a marking signal to the east` line. y

Since no current flows in the branch which connects the local subscribers line to hub |09, the bottom Winding of relay |24 will not be energizedf. Under this condition, as explained above, current flowing through the ltop or biasing windingy of relay |24 maintains the armature of relay |24 in engagement With its left-hand or marking contact. A circuit may then be traced from negative battery through the armature and` lefthand' Contact of relay |24, top Winding of relay |23, right-hand windingof relay |22, contacts of jacks |30 and |3.|, switch |28, which is closed to shunt the open contacts of the transmitting key, Winding of sounder magnet |25, break vcontacts of key |29, resistance |32, contacts of jacks |3| and |30 and through the left-hand winding of relay |22 to positive battery. Magnet' |25 is energized for the marking condition. The armature of relay |23 is maintained in engagement with its left-hander marking contact and the armature of relay |22 remains released as shown for reasons explained.

When a spacing signal is received from the line west, the armature of relay lill is actuated to engage its left-hand or spacing contact. This connects positive battery to the circuit extending through the bottom winding of relay i0?,

actuating the armature of relay H52 to engage with its left-hand or spacing contact.r This disconnects the branch which connects the West line to the hub from the path to negative battery connected to-` the bottom Winding of relay f m3, heretofore traced, and connects the armature of relay |53?. to ground. This in turn causes current to flow' in the other two branches, namely the branch inthe east line and that in the subscribers line through the hub to the ground on the armature of relay |02. As a result of this, the armatures of relays and |124 are actuated to engage their spacing contacts. This rcsults in a spacing signal being impressed on the line east from positive battery through the. lefthand or spacing contact and armature of relay through the top Winding of relay |||l and out over the line. t also results in a spacing signal being impressed on the subscribers loop. The loop isY ordinarily terminated in battery of opposite polarities so that'series-aiding battery is connected to the loop. For the marking condition the loop may be' traced from negative battery connected tothe marking contact of relay1 |24 through the armature of relay |24, top Winding oi relay |23, right-hand Winding of relay |22, contacts of jacks |30 and |3|`, through the switch |28, which shunts the contacts of the transmitting key at thesubscribers station if the circuit is idle or through the closed contacts of' the key, winding of receiving magnet |25, through the continuity contacts of calling-in key |29. variable resistance |32, contacts of jacks |3| and |30, and the left-hand winding of relay E22 to positive battery. Current flows around the loop for the marking condition. When current ilovvs through the bottom Winding of relay |24 due to the vspacing signal from relay |02, as the armature of relay |24 is actuated -to engage with its right-hand or spacing contact, positive battery is connected to both ends of the subscribers loop. Receiving magnet |25 is rel-eased to give a spacing signal at the subscribers station. Relay |22 is deenergized, but the position of its armature remains unchanged. The armature of relay |23 is maintained in engagement with its left-hand contact by current through its bottom Winding. Thus marking and spacing signals may be transmittedfrom the line West to the line east and the local subscribers line simultaneously.

Reception of signals from east Zine The manner in which signals are transmitted from the east line to the West line and the local subscribers line will now be described.

In response to signals received from the east line the armature of relay li is operated between its 'marking and spacing contacts. When a marking signal is received the armature of re'- lay i l@ is in. engagement with its left-hand contact. A` circuit is thus established from negative battery, through the left-hand or marking contact and armature of relay lii, through the bottom winding of relay l2 to ground. The armature ol relay H2 is operated to engage with its right-hand or marking contact. This establishes circuit which has been heretofore traced from hub |132 to negative battery connected to the winding oi relay When negative battery is ccnnected to this branch, since negative battery is connected to the other branches in the hub no currentows in any branch which is the condition for the transmission of a marking signal in eachv branch.

vrwhen a spacing signal is received over the east line, the armature of relay is actuated to engage its right-hand or marking contact. The armature of relay H2 follows this signal. This .connects ground to the branch extending to the hub from the east line. This energizes the -bottoni windings of relays |03 and |94 which reverses the polarities of the batteries connected to the two ends of the transmitting loop of the West line whichv results in a spacing signal being transmitted to the West central station.

Ground connected to the hub |99 from the cest line oi course operates relay |24 in the same manner as ground from the West line.

Reception of signals from local station Zoop When signals are to be transmitted from the subscribers station, switch |28 is opened and the loop is opened and closed by operating the transmittingkey. When the key is opened no current flows in the loop. The armature of relay S23 is actuated, under the inuence of current 'through the bottom winding of relay |23 to engagewith its right-hand lor spacing contact. This connects ground to hub H39 which in turn transmits a spacing signal out over the east and west lines simultaneously.

Transmittmg a Abreak: vsignal engage its spacing contact. If the armature of relay I I I is in engagement with its spacing contact the armature of relay I I0 is operated to its spacing Contact when the armature of relay is next operated to its marking contact. With the armature or" relay I I0 on its spacing Contact, the armature of relay II2 is operated to engage its spacing contact. This connects ground permanently to the hub as when relay I|2 is in engagement with its spacing contact, the path from the hub through the windings of relays |I2 and III is opened and these relays cannot be operated while the armature of relay I I0 remains on its spacing contact. The armature of relay I|2 remains on its spacing contact, which connects ground permanently to the hub as a break signal for the west line and the local loop.

If the west line breaks, ground is permanently connected to the hub from the armature of relay |02. If `the local loop breaks, ground is permanently connected to the hub from the armature of relay I 23.

In the case of a break by the west line or the local loop, the circuit which has been transmitting loses control of the sending relays in the other facilities in much the same manner as described for a break by the east line and it is not considered necessary to explain this in detail for each case.

Calling-in signall for local station loop The concentration group is arranged in such manner that any local station loop forming part of a concentration group may transmit a signal to the central station where the concentration group is being administered to attract the attention of the operator who is administering the concentration.

In order to transmit such a signal, the attendant at the local station operates key |29. This grounds one side of the loop and opens the other side. Relay |22, as has been explained, is arranged so that when the loop is continuous, the eiiect of the current in its rightand left-hand windings is balanced for the marking condition. For the spacing condition no current flows in the loop. When one side of the loop is grounded, the right-hand winding only of relay |22 is energized, operating the armature of relay |22. Ground is connected through the bottom armature and back contact of relay |20, armature and contact of relay |33 and the winding of relay |34 to battery operating relay |34. This in turn lights lamps |35 and |36 as a signal that a party connected through a station loop is calling the operator. In response to the lighted lamp, the operator who is administering the concentration group may connect a cord circuit to jack |39 which cord circuit may in turn be connected to a manual telegraph circuit or a teletypewriter circuit for communication with the station attendant. Connection of a cord circuit to jack |39 will release relay |34 extinguishing the calling-in lamps. This will be described in greater detail in the description below.

Full duplex concentration group CIT manner in. which 'full duplex i communication is provided through two hubs.

In the arrangements per Fig. 2, two four-wire full metallic lines are interconnected through' inverse neutral repeaters located at an'intermediate central station in such manner as.,V to provide two inverse neutral hubs for simultaneous two-way communication between two distant terminals. f

One four-wire full metallic line with its asso ciated repeater and concentration jacks is shown at the left of Fig. 2. It will be assumed that thisl four-wire line extends to a distant terminal to,

the west. A second four-wire full metallic line with its associated repeater and concentration jacks is shown at the right of Fig. 2. It will -be assumed that this four-wire line extends to av west line and the corresponding relays 2I5, 2|6,

2| 'I and 2| 8 in the east line are relays which control the conditioning of the lines for full and half duplex operation, as well as other switching operations, such as adding a line to a concentration group, subtracting a line from a concentration group, substituting another line for a line forming part of a concentration group, etc. at the present time, the manner in which communication proceeds over a full duplex concentration is to be explained. It is pointed out that since the concentration group is already established for full duplex operation and since no additions, subtractions, substitutions, etc. are to be described at this time, relays 205, 206, 201, 208, 2I5, 2I6, 2II and 2|8, which function only while a concentration group is being established and during such switching operations, will remain as shown. Testing relays 209 and 2I0 in the West line and 2| 9 and 220 in the east line will also remain as shown.

i Description of the various relays of the full duplex concentration group Fig. 2 while in the marking condition First the condition of thevarious relays in the repeaters will be described.

During marking, the armature of relay 20| is held in engagement with its left-hand or marking relays 202 and 203 as during the marking inter val negative battery is connected to each end of the circuit extending through these windings. No current flows through the top winding of relay 204 as the circuit through the Winding is broken at the top and bottom back contacts of relay 205. The armatures of relays 2II, 2|2 and 2|3 are held in engagement with their lefthand .or marking contacts. These relays in the east line correspond to relays 20|, 202 and 203 respectively, in the West line and the circuits through them similarly correspond with the circuits through the relays in the west line. The circuit through the top winding of relay 2M is open at the top and bottom front contacts of relay 2|5.

Reception of signals over west Zine As telegraph signals are impressed on the receiving line loop at the distant western terminal, the armature of relay 20| is actuated so as to vengage its marking and spacing contacts alternately. When the armature is in engagement with its left-hand or marking contact, a circuit may be traced from negative battery through the left-hand or marking contact and armature'of relay 20|, through the bottom winding of` relay 204 to ground. The effect of this current actuates the armature of relay 204 so as to engage with its right-hand or marking contact.

When the armature of relay 204 is in engagement with its right-hand or marking contact, a circuit may be traced from negative battery through resistance 223, to top back contact and armature of relay 205, the right-hand or mark- 25 ing contact and armature of relay 2BA, the lefthand outermost armature and .back contact of relay 20B, resistance 224, the armature and contact of relay 2|0 to the hub 225, of the concentration group. From the hub 225, the circuit continues through the back contact and armature of relay 220, resistance 22S, the left-hand middle back contact and armature of relay 2W, resistance 220, bottom back contact and armature of relay 2|5, bottom winding of relay 2HE, 35

bottom winding of relay 2|2 to negative battery. Attention is once more directed to the fact that for the marking condition all branches connected to the hub of the concentration group are terminated in negative battery so that the windings in the path are not energized for the marking condition. When a spacing signal is received over the receiving loop from the distant western terminal, the armature of relay 20| is actuated so as to engage with Vits right-hand or spacing contact. When the armature of relay 20| isV in engagement with right-hand or spacing contact,

a `circuit is closed from positive battery through the right-hand or spacing contact and armature of relay 20| and the bottom winding of relay 2M to ground. The armature of relay 20:1 is ac'tuated so as to engage with its left-hander spacingn con-tact. When the armature of relay 2M moves to its left-hand or spacing contact, ground is connected through the spacing contact and `armatureof relay 204 through the left-hand outermost armature and .back contact of relay '208, resistance 224, armature and contact of relay 2.|,0 to the hub 225 of the concentration group.

Current will therefore flow from negative batterythrough the bottom windings of relays 2|2 and 2|3 toward the hub. The armatures of relays 21,2 :and 2|3 will be actuated so as to engage with their respective right-hand contacts. Thisretive battery to the two loop conductors extending to the distant eastern terminal which rresult in a spacing signal being transmitted to the eastern terminal. As the armature-of relay 22| follows the marking `and spacing signals Vreceived from the vdistant Western terminal over the receiving loop, marking and spacingsignals will be transmitted from relays -2I2 and 2|3 toward the. distant eastern terminal.

The vmanner in which signals are received from the distant eastern terminal and transmitted toward the distant western terminal will now be described. A,

Relay 2|| follows signals received over the re- .5 ceiving group lfrom the distant eastern terminal.

tom 'Winding of relay 2M to ground. This maintains the armature of relay 2|4 engagement with' its right-hand or marking contact. When the armature'of relay 2|ll is in engagement with its right-hand or marking contact, negative battery is connected through 'resistance 221 and the top back contact and armature of relay 2|5, through the right-hand or'marking contact and armature of relay 2M, left-hand outermost armature and back Contact of relay 2|8, resistance 2,25), armature andv contact of relay 2|9 to the hub 230i. From the hub 230, the circuit continues through the contactand armature of relay 209, resistance 23|, left-hand middle back contact and armature of relay 2.08, resistance 232, bottom back contact and armature of relay 205, .bottom windings of relays 23 and 202 to negative battery. Once more it should be observed that negative battery is connected to each branch radiating from the hub point of the concentration group 'for-V the marking condition.

When a spacing signall is received from the dis tant eastern terminal, the armature of relay 2H is actuated to engage with its right-hand or spacing Contact. This connects positive battery through the spacing contact and armature oi relay 2H and the bottom winding of relay 2|l| to ground. The armature of relay 2|4 is actuated to engage with its left-hand'orspacing contact. `When the armature cfrelay 2|4 is in engage- 40 ment with its left-hand or spacing contact, a

circuit may be traced from ground through the left-hand or spacing contact and armature of relay 2I4, thro-ugh the left-hand outermost armature and back contact of relay 2|8, resistance 229,- armature and contact ci relay 219 to the hub 2.30.` This operates relays 202 and 203 so that their armatures engage their right-hand or spacing contacts. lWhen the armatures of relays 22 and. 203- are in engagement with their right-hand or spacing contacts, the battery connections to the loop extending to the distant `western terminal are reversed and a spacing signal is thereby transmitted to the distant western terminal.

The above explains how telegraph signals may beA transmitted between two distant terminals through inverse neutral repeaters located at an intermediate telegraph station on a full duplex basis. v ,l i

The jacks shown-at the bottom of Fig. 2 are provided to facilitate switching operations such as adding a line to the concentration group, subtracting a line from the concentration group or substituting a line for a line forming part of a vconcentration group. These jacks also provided verses the connections .from positive and mega ri; for disconnecting a line from a concentration 7.0 General description .ofi the teletypew'riter cord circuit per Fig. 3

' Fig. 3 is a double ended cord circuit known as a teletypewriter cord. circuit with two flexible V 7.5 cords and two plugs rwhich cooperate with the as follows:

1. When the plug is inserted in the appropriate jack `ofr Fig. 1, with all keys normal, it is 'possible to monitor on a half duplex concentration.

2. When the plug 30| is inserted in the appropriate jack of Fig. 1 and key 303 is operated, it is possible to communicate by means of the tele-A typewriter per Fig. 4 over the half duplex concentration.

3. When plug 30| is inserted in the appropriate jack of Fig. 1, it is possible to split a leg of the concentration group from the hub by operating key 304 or 305.

4. When the circuits are arranged as described yunder 3 above and key 303 is operated, it is possible to communicate over the leg Which has been split from the concentration group or to communicate over the circuits remaining in the concentration group by means of the teletypewriter -circuit of Fig. 4. By operating key 306 instead of key 303, it is possible to communicate over these facilities by means of the manual telegraph circuit of Fig. 5.

5. When the circuits are arranged as described under 3, above, the supervisory lamp 301 in Fig. 3 responds to signals on the leg when communicating with the hub or signals on the hub While communicating With the leg.

6. When this circuit is used for telegraph or teletypewriter communication over a local trunk to supervisor (not shown in this application) or when it is used to answer the calling-in signal at an answering jack, such as |38 or |39 in Fig. 1,

th'e circuit is arranged to register on the supervisory lamp any supervision signals that may be received over the local trunk or from the concentration group.

7. When the plug 302 of this circuit is inserted in the appropriate jack in one concentration jack circuit per Fig. 2 and the plug 30| into a similar jack of a second concentration jack circuit, this circuit is arranged to permit full duplex communication.

8. Under the condition described in '7, above, the rear cord associated with plug 30| is used for receiving and the front cord associated with plug 302 is used for sending signals.

9. Under the condition described in 7, above, the operation of key 308 will permit the front cord to be used for receiving and the rear cord for sending signals.

10. Under the condition described in 7, above, the operation of key 304 or 305 will split the associated leg from the hub.

11. Under the condition described under 10, above, the operation of key 303 or of key 306 is arranged to permit teletypewriter or manual telegraph signal communication on a full duplex basis on the legs or on the hubs.

12. The rear cord of this circuit is arranged to permit tip-busy test through plug 30|. A busy condition is indicated by the lighting-of the common positional busy lamp 309.

Monitoring onhalf duplex facilities Refer now to Figs. 1, 3, 4 and 5 arranged as indicated in Fig. 6.

The left-hand cord of the teletypewriter cord circuit per Fig. 3 is arranged to permit monitoring on half duplex teletypewriter facilities such as shown in Fig. 1. If plug 30| associated with the left-hand cord is inserted'into a jack arranged for monitoring such asl42 or |43, and all keys shown in Fig. 3 are in their normal position, relay 3|0 in Fig. 3 is operated. The circuit for this may be traced from battery through the Winding of relay 3|0, the back contact associated with the bottom armature of key 303, through said armature, the back contact and bottom armature of key 305, the back contact and top armature of key 305, the back contact and top armature of key 304 to the sleeve of plug 30| Which meets ground connected through the lov-r resistance Winding of relay |08 to the sleeve of the above-mentioned monitoring jacks. If it is preferred, connection may be made for monitoring to the leg multiple jacks such as |40 and |4l. The winding of relay 3|0 is of high resistance to prevent interference with the established sleeve conditions when connection is made to a leg multiple jack. Operation of the splitting key 304 or 305 While monitoring in jacks such as |42 or |43 may seriously interfere with the circuit monitored upon. When monitoring, the operation of relay 3|0 in turn operates relay 3| over a circuit from ground through the armature and front contact of relay 3|0, through the winding of relay 3|| to battery. Operation of relay 3| closes the tip circuit extending from plug 30| which is connected to a transmission conductor in the half duplex concentration group per Fig. 1, through the tip of the jack with which it is associated, through to the attendants teletypewriter circuit.

It will be assumed that plug 30| has been inserted into jack |42. The tip of jack |42 is connected to the hub |09, through the armature and contact of relay |08. Communication signals through the hub |09 will be passed through the tip `of jack |42 to a circuit extending from the tip of plug 30| through the top armature and front contact of relay 3| I, through the top inner back contact and armature of relay 3|2, through the top middle back contact and armature of relay 3|3, through conductor 316 into Fig. 4. The leads extending to the right of Fig. 3 connect with corresponding leads in alignment at the left of Figs. 4 and 5. Conductor 3|6 in Fig. 3 connects with lead 4|6 in Fig. 4 and extends through the top middle back contact and armature of relay 40| to the grid of vacuum tube 402. The operation of relay 3|| closes a circuit from ground through its bottom armature and front contact over conductor 3|1 in Fig. 3 which connects to conductor 4|`| in Fig. 4. The circuit then extends through the top continuity contacts of relay 40|, through the winding of relay 405 to battery, operating yrelay 405. This conditions the teletypewriters set to receive teletypewriter signals from the half duplex concentration group per Fig. 1 for monitoring ina manner which will now be described.

The operation of relay 405 closes a'circuitffrom ground through the bottom armature and front contact of relay 405, resistance 403, ballast lamp 404 and the lament of tube v402 to grounded battery, heating the lament of tube 402. The

bottom Winding of relay 401 maintains the armature of relay 401 in engagement With its leftyhand or'marking contact. The operation of relay t5 also closes a circuit from ground through lthe top inner armature and front contact of relay 405'and the Winding of relay 403 to battery, operating relayy 409. The operation of relay 409 supplies power to the teletypewriter motor 4|0, through the top andbottom armatures and cooperatin'gicontacts of relay 40S, to the motor windings. i This Starts the motor.

The output circuit of Vacuum tube 402 may be traced frompositive battery, through resistance 40,8, the top'winding of relay 401, resistances 4|| and 4|2, to the anode of tube 43|, and thence through the cathode of tube 402 to ground.

It has been explained in the description of the operation of an inverse neutral concentration circuit that the branches radiating from a hub are all normally terminated in negative battery for the marking condition. Negative potential will, therefore, be impressed between the grid and grounded cathode of tube 402 While the marking condition obtains in the concentration circuit. It has also been explained that when a spacing signal is transmitted through an inverse yneutral circuit, ground is connected to the hub of concentration. `For a spacing signal, therefore, the grid of tube 402 Will be grounded. For the marking condition, therefore, While negative potential is impressed between the grid and cathode of tube 402 no current Will flow through the top Winding of relay 401 and the armature of relay 401 will be held in engagement with its left-hand or marking Contact under the influence of current flowing through the bottom Winding.l 'When a spacing signal is transmitted through the concentration group and the grid of tube402 is grounded, sunicient current will flow through the top winding of relay 401 to actuate the armature of relay 401 to the right. While the circuit per Fig. 4 is in use, the attendants teletypewriter apparatus Will be connected to jacks 4|3 and M4 by means of plugs 4|5 and1 M3. While these connections are established andthe marking condition prevails, a oircuit may be traced from positive battery through resistance M0, the armature of relay 401, marling contact of relay 401, the sleeve of jack 4|4, sleeve of plug 4|3, receiving magnet 420, sleeve of plug 42|, sleeve of jack M3 through the bottom armature and make :contact of jack springs M3, which are closed, and resistance 422 to negative battery. When the armature of relay 401 is actuated 'to the right in response to a spacing signal this circuit is broken.. The receiving magnet420 will, therefore, follow the marking and spacing signals transmitted through the concentration group circuit.

Communz'catzon between theuttendants teletypewm'ter set and the concentration group 'When plug ses of the com circuit of Fig. 3 is inserted into an appropriate jack, such as jack |42, associated with the half duplex' concentration group per Fig. 1 and key 303 in Fig. 3 is operated, a circuit is established from battery, through resistance 3|8, top Winding of relay 3|9, resistanc'e320, winding of relay 32|, bottom front contact andlovver armature of key 333', bottom back Contact and bottom armature of key 303,.

top back contact and top armature of key 3.05, top back contact and top armature of key 304, tothe sleeve of plug 30|.Y From the sleeve of plug 30|, the circuit extends through the sleeve of jack |42 in the concentration group circuit per Fig. 1 to ground through'the low resistance Winding of relay |03. As the cooperating jack sleeve circuit is of 10W resistance, the armature of relay 3|9 Will be actuated to the right due to the effect of current through its top Winding. Relay v32| Voperates in all'cases closing a circuit through'the bottom winding of relay 3|9. But the effect of current through the bottom Winding of relay 3|9 tending to maintain the -arrnature of relay 313 in engagement with its lefthand contact is less than the effect of current in the top winding when the resistance of the sleeve circuit of the jack with which plug 33|- cooperates in Fig. l is low. The operation of relay 32| causes the operation of relay 3H from ground through the top armature and front contact of relay 32|, through the Winding of relay 3||to battery. The operation of key 303 operates relay 3|5 over a e circuit extending from ground through thetop armature and iront contact of key 333, through the Winding of relay 3|5 to battery.

vIt 'should be pointed out at this point that a plurality of teletypewriter cord circuits per Fig. 3 aswell as other cord Circuits are located at each operators position, Whereas only one attendants teletypewriter set circuit per Fig. 4 and one attendants manual telegraph set circuit per Fig. 5 are provided. The single attendants teletypewriter y set and the single attendants manual telegraph set per Figs. 4 and 5 are connected individually to any of these cords as may be-required. In order to guard against the connection of Fig. 4 or Fig. 5 to more than one cord circuit ata time, a chain circuit is provided through the Various cord circuits. The chain circuit is used to control the connection of the single attendants teletypewriter set or the single attendants telegraph set to one cord only. It extends sequentially through the armatures and contacts of keys corresponding to keys 303 and 306 in each cord. It is by means of these keys that ground is applied to relays such as relay 3|5 or relay 322 which are individual to each cord. If aekey corresponding to key 303 or key 336 in a preferential position in its chain circuit is operated, a relay corresponding to relay 3|5 or relay 322 in the corresponding circuit will be operated to connect the attendants teletypewriter set or attendants manual telegraph set to said circuit. In such case, the operation of a key corresponding to key 303 or key 306 in a teletype- Writer cord circuit more remote from ground will not be availing to operate the corresponding relays 3|5 and 322 as the path to ground will be broken Where the key is operated. In this manner, the connection of the attendants teletypewriter set per Fig. 4 or the attendants manual telegraph set per Fig. 5 through parallel branches to a plurality of cords is avoided.

The operation of relay 3|5 operates relay 40| from ground through the bottom outer armature' conductor 423 in Fig. 4 which extends through the armature of relay 425. When the armature of relay 425 is on its spacing contact and plug 4|8 is inserted in jack 4|4, the circuit is continued through the bottom armature and front contact of jack 4|4 to ground. Conductor 324 in Fig. 3 connects to conductor 424 in Fig. 4 and the circuit extends through the top middle front contact and armature of relay 40 l, Which is operated, to the control grid of vacuum tube 402.

This circuit controls the reception of communication signals through the teletypewriter receiving magnet 420 in the same manner as described above for the monitoring operation. Conductors 323 and 423 form a part of the transmitting circuit, by means of which signals may be sent y from the teletypewriter sending contacts in Fig. 4 which control the operation of relay 425.

The operation of relay 40| transfers the path extending from ground on relay 3| through the top continuity contacts of relay 40|, to the Windin g of relay 405. After the operation of relay 40| relay 405 is held operated over a path from battery through the winding of relay 405, through the top innermost make contact and armature of the top continuity contact combination of relay 40|, over conductor 421, which connects to conductor 321 in Fig. 3, through the top innermost make contact and armature of relay 3|5 and the bottom make contact and armature of relay 3| to ground.

Relay 405 operated performs the same functions as described in the monitoring operation above.

During the period that Fig. 4 is not arranged to transmit, relays 40| and 43| are released.

While so released, a circuit may be traced from negative battery through resistance 423, top winding of relay 425 and resistance 429 to a parallel circuit, one branch of which extends to ground through the bottom continuity contacts of relay 40| and the other branch of which extends also to ground through the bottom back contact and armature of relay 43 The effect of current flowing in this circuit maintains the armature of relay 425 actuated to the left or marking position. This prevents ground from being connected from the bottom front contact of jack 4| 4 to the transmission conductor.

The operation of relay 40| establishes a circuit which extends from ground through the bottom front contact and armature of relay 40 I, through the tip of jack 4|3 and tip of plug 4|5, through the teletypeWriter sending contacts, through the tip of plug 4|8 and tip of jack 4|4, through the top or line Winding of relay 425 and resistance 428 to negative battery. The operation of relay 40| further disconnects ground from the circuit which extended through the bottom continuity contacts of relay 40| and resistance 4 29 and through the top or line Winding of relay 425 to negative battery. The operation of relay 40| further establishes a circuit from ground through the top outermost armature and front contact of relay 40 through thermistor 430, the winding of relay 43| and resistance 4 32 to negative battery;

When ground is connected to the winding of relay 43| by the operation of relay 40|, current builds up slowly in the Winding of relay 43|, due to the action of the thermistor 430. The mini-A mum time in which the 43| relay can operate is 600 milliseconds. This delay insures at least one revolution of the sending contact cam on the teletypewriter after relay 409 operates, before the bleeder circuit through the top Winding of relay 425 to ground through the armature and back contact of relay 430 is broken and the biasing circuit, through the bottom winding of the sending relay 425 which tends to operate the armature of relay 425 to its right-hand or spacing contact is closed through the make contact of relay 43|. If the latch on the teletypewriter is standing open at the instant of the operation of relay 40|, the operation of the circuit, as described above, prevents the transmission of a false signal before the rst closure of the latch.

Transmission from the teletypewriter facility is accomplished by operation of the teletype- Writer keyboard. Relay 425 follows the teletype- Writer signals. The opening of the teletypewriter contacts permits the armature of relay 425 to operate to engage its right-hand or spacing contact under the influence of current in the bottom winding of relay 425. This results in the connection of ground from the bottom front contact and armature of jack 4| 4, through the right-hand or spacing Contact and armature of relay 425 and over conductors 423 and 323 by a path heretofore traced, to the tip circuit which connects to the communication conductor in the half duplex concentration group. Half duplex reception and transmission can, therefore, take place through the teletypewriter cord circuit and the attendants teletypewriter set circuit.

At the conclusion of communication, plug 30| is disconnected from jack |42 and key 303 is restored to its normal position. Relay 3|5 will release as ground is disconnected from the circuit through its Winding at the top back contact of key 303. The release of relay 3|5 in Fig. 3, in turn, permits relay 40| in Flig. 4 to release as ground is disconnected from the path through the Winding of relay 40| at the bottom outer back contact of relay 3| 5. Relay 32| is released, in turn releasing relay 3||. Relay 3|9 will also release. With relay 3|| released, relay 405 in Fig. 4 Will be released as ground is disconnected at the lower armature and make contact of relay SII. Relay 43| will also release upon the release of relay 40| as ground is removed from the winding of relay 43| at the top outer armature and front contact of relay 40|. Relays 401 and 425 will return to their normal idle condition upon the release of relays 40| and 405. The circuit through the filament of vacuum tube 402 will be broken upon the release of relay 405 unless key 433 has been operated. Key 433 is known as a position filament key. When it is operated, current is supplied to the lament over a circuit from battery through the lament of tube 402, filament of lamp 404, resistance 434 and key 433 to ground. Resistance 434 is of higher value than resistance 403. This resistance is chosen so that the current through the tube 402, when key 433 is operated, is sufficient to keep the ilament partially heated in order to minimize the time required to heat the lament after relay 405 is operated.

Supervision of half duplex concentration groups The circuits of this invention are arranged in.

verses the connections of.th'e.attendants.tele typewriterl 'set circuit to theteletypewriter cord circuit and permits. reception of. signals over the cord associated with' plug 302'and the transmission of signals over thev cord associatedwith plug vAt the conclusion `of communication the withdrawal of both cords vfrom ltheir respective jacks and the restoration of such keys as are operated causes the release of all operated relays and returns ther circuits tonormal.

e Manual telegraph communication v The teletlfpewriter cord circuit, per Fig. 3, may `be connected *toy the attendants fmanual telegraph set, Vper Fig. 5, which provides facilities for manual telegraph communication 'over a concentration group Whenthe cord associated with plug 30| is connected to the appropriate jack. It will be assumed that plug 30| of Fig. 3

is inserted into jack of Fig, 1. Key 306 is operated. This closes a circuit vfrom ground through. the top armature and front -contact'of key 306 and the Winding ofv relay 322I to battery, operating relay 322. It Ashould Ybe pointed out that .the circuit throughfthe contacts tofj key 300 by means of Which relay: 322A; operated is a chain circuit and extends through the armaturesand contacts of a plurality of similar keys in other cord circuits at the positionwherethe concentrationk group is being administered. HIi' a key in a preferential position in the series circuit, that is to say, closer to the sourcetof ground, is already operated,`the attendants manual telegraph setcircuit, per Fig. .5, vi ill,`r er associated with said circuit and since the chainl toy ground i' Will be broken in said circuit, it will beimpossible to operaterelay 322m' the circuit more remote from the ground source. The object of this is to preventthe connection of theusingle attendants manual telegraph set circuityper, Fig. 5, to more than one cord, per Fig. 3,y ,atione time. The insertion of plug 30|y into jackt|40 causes the operation of relays 32|, 319 and 3|| in the same manner as described heretofore. The path from the tip ofwplug 30| is divided into two branches in the same manner as described for the operation'of the cord, per Fig. 3, with the attendants .teletypewriter set, per Fig.` 4. Conductor 332 in Fig. 3v isv joined toconductor 532 in Fig. 5. Relayl in Fig. 5 is operated over a path extending fromthe bottom outermost armature andfront contact of relay 322` through the winding` of relay 50| to battery. The path from conductor. 532'is then extended through the top outer'armature and front contact of relay 50| to the control grid of vacuum tube 502. Conductor" 333 Which is joined to the tip of plug 30| in parallel with conductor 332 in the'same manner as described above extends through conductor 533 in Fig. 5 tothe armaturerofrelay 525. Vacuum tuben502 operates in the same manner as vacuum tube 4072 described above. Relay 501 follows the signals received from the concentration groupand impresses them on the receiving magnet520 associated With the sounder. Relay 525follows the signals transmitted from the .attendants telegraph set. These signals are impressed on the transmission conductor in the concentrationv -group over' the circuit which extends to the tip of the plug 30| inFig. 3. The general similarity of Fig. 5 and Fig. 4, except forV the Obvious differences necessary to equip one With a teletypewriterl andthe 'other with a Morse key and sounder, -is such that it does not appear necessary to ldescribe the` operai tion.of-Fig. 5 in-iany greater detail as its opera-l tionwvvill be apparent from the description of Fig above.

. Splitting lco'11.cen1r1tio'n groups ecircuits. herein are arranged in such a mannerfthat it is possible to disconnect any de.- sired facility lforming part of a particular con-- centration group from the group. It is possible: to communicate over the facility which has been; splitfoff. from the group While excluding thosefac'ilitiesg' still interconnected in the group from the communication. Alternatively it is possible to communicate with thegroup While excluding the facility Which has been split olf. While com.- munication is in progress either with the separated facilityor With the group, the circuitsI are arranged so'thatv the supervisory lamp in the cord is flashed in response to signals on the group iffthe communication is in progress With a sep-- arat'edffacility or on the separated facility if communication is in progresswith the group.. The'manner'in which this is performed will now' be described. .It'will be assumed that the circuits are ar ranged as shown in Fig. 6 and that plug 30| of.' Fig.'3is .inserted into jack |42. If it is desiredA toisplit aparticular leg yfrom a concentration. group, key305 is operated. In order to com-- munic'ata'key 303 or key 306 is also operated.. A'circuit'is closedfrom ground through the bot-- tmarmature and front contact of key 305,. through the winding of relay 334 to battery, operatingrelay-334. It will be assumed that key' 303' is yoperated which in turn operates relay 3|5? tofconnect "the attendants teletypewriter set per' Fig. 5to the cord, per Fig. 3. The operation of re lay 334' closesacircuit through its bottom arma .ture 'andfront'contact and the Winding of relay 335? 'to battery, operating relay 335.4 A circuit. may be traced from ground through the winding: ofrelay |08,'sleeve of jack |42, sleeve of plug 30| to aparallel circuit. One branch of the parallel circuit extends through the bottom outer front contact and armature of relay 335 to junction point 340. Thesecond branch extends through the top armatureand break contact of key 304, through the top'armature and front contact of key 305 to junction point 340. The branches join and .the path continues through the winding of :relay32|,through resistance 320 to the bottom inner armature and front contact of relay .335 directly to battery. The resistance of this path to battery is less'than the resistance of the sleeve circuit to battery' When the circuit is arranged for communication but when the splitting keysfare not' operated'. Under such circumstances, the path to battery, which has been heretofore traced,` extends through the top Winding otr-clayv 3|9 and resistance 3|8 after passing Itl'irou'g'h'resistance 320. When the resistance of 'the 'sleeve' circuit is low, relay |08 operates. The operation of relay |08 disconnects the West line from the hub by opening the circuit extending froml the west-line through resistance |01 at the armature andback contact of relay |08. The communication branch from the West line, however, is connected to the tipof jack |42. The ring 'ofjack- |42'is connected to the hub |09. This operation, therefore, arranges the circuits so that it ispossible'to communicate either by teletype- .writer or; if key 30B is operated instead of key 303,:by vmanual ltelegraph as described above over the tip conductor of jack- |42 with the west line. At the same :time signals on the facilities which are still associated together in the concentration group will be passed through the hub and the ring spring of jack |42, through the ring of plug 30|, bottom back contact and armature of relay 328, bottom outer back contact and armature of relay 3|3, bot-tom inner armature and front contact of relay 3i5, armature and left-hand contact of relay 3| 9, the winding of relay329 and resistance 330 to battery, vto operate relay 329 intermittently, which results in irregular hashing of the supervisory lamp 301. It should be observed that as the top winding of relay 3|9 is shunted, the armature of relay 3|9 Will be held in engagement with its left-hand contact by the eiect of current through its bottom winding.

If it is desired, instead of communicating with the facility which is split off, to communicate With the facilities which still remain interconnected in the concentration group, key 304 is operated. This closes a circuit from ground through thev bottom armature and front contact of key 304 and the winding of relay 3|3 to battery, operating relay 3 i3. The operation of relay 3|3, in turn, closes a circuit for the operation of relay 335. This circuit may be traced from ground through the top innermost armature and front contact of relay 3 3, through the winding of relay to battery. The operation of relay 335 results, as We have seen, in the reduction of the resistance in the sleeve circuit of Fig. 3 and the operation of relay |08, which splits the West line from the hub. It also shunts the top Winding of relay 3|9. In this case, however, the circuits are arranged so that it is possible to communicate with the circuits which still remain interconnected in the concentration group rather than with the facility which has been split off from the group. This communication With the concentration group takes place over the ring circuits of plug 39| and jack |42. The circuit extends from the hub |09 through 'the ring of jack |42, ring of plug 39|, bottom back contact and armature of relay 328, top middle front contact and armature of relay 3|3 to the circuit which extends into the attendants teletypewriter set or the attendants manual telegraph set which has' heretofore been traced. In this case also communication signals on the facility which has been split oi from the concentration willv result in the irregular dashing of lamp 301. This occurs from signals on the tip. The circuit may be traced from the tip of jack |42, through the tip of plug 30|, 'top armature and front contact of relay 3| top inner back contact and armature of relay 3 2, bottom inner front contact and armature ofrelay 3|3, top back contact and armature of relay 334, through the Winding of relay 329 and resistance 330 to battery.

If Figs. 3, 4 and are being used in connection with a full duplex concentration group, such as Fig. as per Fig. "l, plug 30| is inserted into ask est' andV pine, au is inserted. int@ jack 23a. If keys 305 and are operated, relays 334 and 3|5 will be operated as described above.` The operation of relay will cause the operation of relay 335 also described above. This results in the reduction of the resistance of the sleeve circuits of Fig. 3 connected'to both jack 234 and jack 233. The change for the sleeve associated with plug 39|. is the same as heretofore described. In the case of the sleeve circuit associated with plug 302, the operation. of relay 335 shunts the path which previously extended to negative battery through the high resistance botbe operated very quickly.

tom Winding of relay 3|4 and connects it instead directly t'o negative battery through the top armature and front contact of relay 335. Under these circumstances relay 2li) and relay 209 will both operate. The operation of relay 2|0 will disconnect the receiving circuit for the West line from hub 225. The operation of relay 209 will disconnect the sending circuit for the West line from hub 230.

As a result of these operations, the receiving and transmitting circuits for the West line, per Fig. 2, are disconnected from their respective hubs 225 and 230. The transmitting conductors giving access to the receiving and transmitting branches of the West line are connected to the tip of jack 234 and the tip of jack 233, respectively. The ring circuit of jack 234 is connected to the hub 225 and the ring circuit of jack 233 is connected to the hub 230. The receiving circuit of the west line is extended over the tip of jack 30| through a path already traced to the transmitting and receiving branches of the attendants teletypewriter set, per Fig. 4, or the attendants manual telegraph set, per Fig. 5, if key 306 is operated. The sending circuit i'or the west line is connected through the tip of jack 233 and of plug 302 into Fig. 4 and Fig. 5 over a path which has also been heretofore traced.

By this means it is possible to communicate over the West line. Signals from the east line meanwhile are impressed through the ring circuit of vjack 233 and plug 302 on relay 329 which operates to ash lamp 301 irregularly as an indication of this condition. If key 394 is oper ated instead of key 305, relay 3|3 is operated. The operation of relay 3|3, in turn, operates relay 335. The reduction of the resistance of the sleeve circuits associated with plugs 30! and 302 results from this operation. Relays 209 and 2|!! will be operated due to the low resistance cord sleeve circuit in each instance. In this case, however, the ring circuit of jacks 233 and 234 will both be extended over paths heretofore traced into Figs. 4 and 5 While the tip circuit i-n each instance Will be' connected through the Winding of the supervisory relay 329. It is then possible to communicate from Figs. 4 and 5 through the hubs 225 and 230. Signals arising in the West line Will be impressed on the winding of relay 329 resulting in the irregular flashing of lamp 301.

The operation of key 309 operates relay 352 as described above, and releases relay 328. This reverses the connection of the front and rear cords to the sending and receiving elements of the circuits per Fig. 4 and Fig. 5 as well as to relay 329.

Restoration of the particular split key, key 304 or 305 which has been operated, causes the release of relays 334 and 335 or 3|3 and 335 as the case may be and returns the cord sleeve or sleeves to the high resistance condition. This, in turn, causes the release of relays such as 209 and 2I0 in Fig. 2 and restores the concentration group to normal.

If in changing Vfrom the split-twleg to the split-to-hub condition it is not desirable to have the leg make contact with the hub, the key lever of key 304 or 305, as the case may be, should If the key lever is operated quickly enough and Without tumbling, relay 335 does not release and the leg remains split from the group due to the fact that the low cord sleeve resistance remains unchanged. At

the conclusion of communication the withdrawal of the plug or plugs and the restoration of all operated keys releases all operated relays returning the circuit to normal.

Busy test feature The cord circuit, per Fig. 3, is arranged so that it will give an indication of a busy condition existing on a trunk with which Fig. 3 cooperates. Although the cooperating trunk circuits, such as interoce and local telegraph trunks, are not disclosed in this application as they are not per se a part of this invention, it is to be understood that the cord, per Fig. 3, is arranged to cooperate with facilities other than those described herein, such as interofce and local telegraph trunks. Fig. 3 is arranged in such a manner that if the tip of plug 30| is connected to a jack having battery potential on the sleeve, a circuit is closed from said sleeve through the tip of jack 30| and the top armature and back contact of relay 3| l through the winding of relay 336. This results in the actuation of the armature of relay 336 to engage with its right-hand contact resulting in the lighting of lamp 339 over an ob'- vious circuit.

What is claimed is:

1. In a telegraph switching system in combination, a hub type telegraph repeater concentration group comprising a plurality of telegraph circuits interconnected through hub type repeaters, a cord circuit, means in said cord circuit for forming. an operable telegraph path through said cord and said concentration group, an attendants teletypewriter circuit including means for communicating through said cord circuit to said concentration group.

2. In a telegraph switching system, a plurality of hub type telegraph repeaters interconnected to form a concentration group, a cord circuit, an attendants manual telegraph set circuit, and uneans in said circuits and said group for establishing an operable telegraph path from said set through said cord and through said group.

3. In a telegraph switching system, a plurality of hub type telegraph repeaters interconnected to form a concentration group, a cord circuit, means in said circuit for cooperating with said group, an `attendants teletypewriter set circuit, means in said cord circuit for severing a telegraph branch forming part of said concentration group from said group and means for connecting said severed branch through said cord circuit to said attendants teletypewriter set circuit, to form an operable telegraph path.

4. In a telegraph switching system, a hub type repeater telegraph concentration group, a cord circuit, means in said circuit for cooperating with said group and means in said cord circuit responsive to the connection of said cord circuit to said concentration group for disassociating a branch of said group from said group.

5. In a telegraph switching system, a hub type telegraph repeater concentration group, a cord circuit, means in said cord circuit for interconnecting said cord circuit and said group, telegraph communication means connectable to said cord circuit and supervisory signal means in said cord circuit, independent of said communication means, responsive to signals from said group.

6. In a telegraph system, a hub type telegraph repeater concentration group, a cord circuit, means for connecting said cord circuit to said group, and means in said cord circuit and said group for splitting a facility from said group after said connection.

'7. In a telegraph switching system, a hub type telegraph repeater concentration group, comprising a plurality of telegraph circuits interconnected through individual inverse neutral repeaters to a common hub, a cord circuit, means in said circuit for interconnecting said cord circuit and said group, means for severing a circuit forming a part of said group from said group, a telegraph transmitter and means in said circuits for associating said transmitter with the circuit so severed.

8. In a telegraph switching system, a hub type telegraph repeater concentration group, a cord circuit, means in said circuit for connecting said cord circuit and said group, means for severing a repeater forming a part of said group from said group, a telegraph transmitter, means in said circuits for associating said transmitter with said group and means in said circuit for excluding said severed repeater from said transmitter during said association.

9. In a telegraph switching system, a, hub type repeater concentration group, a cord circuit, means for interconnecting said cord circuit and said group, a telegraph receiver, means for associating said receiver through said cord circuit with said group, means in said cord circuit for severing 4.a repeater forming part of said group from said group and means for connecting said receiver exclusively to said severed repeater.

10. In a telegraph switching system, a hub type telegraph repeater concentration group comprising a plurality of telegraph lines interconnected through hub type telegraph repeaters to a common hub, a cord circuit, means for interconnecting said cord circuit and said group, an attendants teletypewriter set, an attendants manual telegraph set, means for directly connecting either set through said cord with said group and means in said group, said cord circuit and said sets for selectively establishing operable telegraph paths interconnecting said sets and said group.

11. Two hub type telegraph repeater concentration groups, a double ended cord circuit, means for interconnecting said cord circuit and said groups, means in said cord circuit for selectively associating an attendants teletypewriter set or an attendants telegraph set through said cord circuit with said groups and means for communicating through said cord circuit between either of said sets and said groups at separate times.

l2. In a telegraph system, in combination, a hub type telegraph repeater concentration group, a teletypewriter cord circuit, means for interconnecting said circuit and said group, means for transmitting and receiving telegraph communication signals through said cord circuit and said group while so connected, a supervisory signal in said cord circuit independent of said communication means and means in said circuit responsive to control means in said group for operating said signal to attract the operators attention to said group.

13. A hub type telegraph repeater concentration group, a cord circuit, means for interconnecting said cord circuit and said group, and means in said interconnection for conditioning said interconnection for communication exclusively over a single telegraph branch forming, part of said group and over said cord circuit.

14. A hub type telegraph repeater concentration group, a cord circuit connected thereto, means in said cord circuit for disassociating a repeater forming part of said group from said group, a teletypewriter printer, means for connecting said printer through said cord circuit to said group, means for communicating exclusively between said printer and said disassociated repeater and means for communicating between said printer and said group while excluding said repeater.

15. In a telegraph system, `a hub type telegraph concentration group comprising, :a plurality of telegraph lines interconnected through individual hub type repeaters to a telegraph hub, a cord.

circuit, means for interconnecting said cord circuit and said group, a, telegraph transmitting and receiving printer and a manual telegraph set, means for selectively interconnecting said printer or said set through said cord circuit with said group, means in said group, responsive to control means in said cord circuit, for severing a line forming part of said group from said group, means for communicating either between said severed line and said printer or said set or between said group and said printer or said set while excluding said severed line and means in said cord circuit for receiving supervisory signals from the portion of said concentration -group not at the moment arranged for communication with either said printer or said set.

16. A hub type telegraph repeater con/centration group, a cord circuit including means for cooperating with said group, .a teletypewriter transmitting and receiving printer, a manual telegraph set, means in said cord circuit for selectively connecting either said printer or said set through said cord circuit with said group, means also in said cord circuit for severing a repeater forming part of said group from said group and means for communicating, between said printer or said set, through said cord circuit with either said severed repeater or the repeaters remaining associated in said group.

17. In a teletypewriter switching system, a telegraph cord circuit, a communication conductor extending from a flexible connection in said cord circuit through said cord circuit to parallel branches in an Iattendants teletypewriter set circuit, a space discharge device in one of said branches, a polar relay having a winding in series with the output circuit of said device, a telea typewriter receiving magnet responsive to said relay, and a polar relay in the other of said branches responsive to teletypewriter sending contacts,

Cil

18. In a teletypewriter switching system, a teletypewriter, transmitting contacts thereon, a telegraph relay, means or controlling said relay in response to the operation of said contacts, and time delay means for preventing the response of said relay to said cont-acts for an interval.

19. In a teletypewriter switching system, a teletypewriter transmitting circuit including a teletypewriter transmitter having transmitting contacts thereon normally Iclosed when idle, a polar telegraph transmitting relay responsive to said contacts, said relay having a rst winding in series with said contacts, means for energizing said winding when said transmitter is conditioned for transmitting to place said relay in the marking condition, a second winding on said relay, means for energizing said second winding to oppose the innuence of said lrst winding when said relay is conditioned for transmitting, and means for delaying the energization of said second winding for an interval to insure the closure of said contacts and the energization of said rst winding when said transmitter is being conditioned for transmitting, to prevent the transmission of a false signal during the conditioning interval.

20. In a teletypewriter switching system, a plurality of telegraph repeaters interconnected through a common neutral point, a teletypewriter transmitting circuit, means for connecting said circuit to said neutral point, a polar telegraph transmitting relay responsive to teletypewriter transmitting contacts in said circuit, means, including contacts on said relay, for transmitting telegraph signals from said relay through said neutral point to said plurality of repeaters in response to the actuation of said teletypewriter contacts, and means for preventing the transmission of false signals by said relay due to the false operation of said teletypewriter contacts when said teletypewriter is first started.

21. Ina teletypewriter switching system, a telegraph transmitting relay, a teletypewriter transmitter, contacts on said teletypewriter controlling said relay, a motor for operating said teletype- Writer and said contacts, and electromagnetic means for preventing the operation of said relay as said motor is started when said contacts have been stopped in. an abnormal position.

WAYNE V. K. LARGE. CHARLES W. LUCEK. TOLA A, MARSHALL. 

